HONG KONG (Reuters) - China’s biggest chipmaker SMIC said on Wednesday its board is aware that Mong-song Liang intends to resign from his co-chief executive role. The company is working actively to verify Liang’s plans to leave, Semiconductor Manufacturing International Corporation said in a filing to the Shanghai stock exchange. A letter of resignation purportedly from Liang began circulating online late on Tuesday in which he stated the reasons for his departure. Reuters could not reach Liang to verify the letter, and SMIC did not reply to a request for comment. Liang was appointed SMIC’s co-CEO alongside Zhao Haijun in 2017. SMIC is a key player in China’s efforts to build up its semiconductor supply chain but has come under pressure this year from the Trump administration, which curbed U.S. companies from supplying it with goods and services. Semiconductor industry analyst Mark Li of Bernstein Research described Liang’s pending resignation as a “setback” for the company’s future technology progress. Shares of SMIC on Shanghai’s STAR Market, where it listed this year, fell by nearly 10% after trading opened on Wednesday. Trading was halted for the company’s shares in Hong Kong. SMIC was expected to more than double its spending this year to make higher-end chips but said last month it would reduce its expenditure plan because of the U.S. export controls. The U.S. also added SMIC and other Chinese companies to a blacklist of alleged Chinese military companies this month, a move that will prevent U.S. investors from buying the firms’ securities from late next year. A former top staffer of Taiwan Semiconductor Manufacturing Co Ltd, SMIC’s chief rival, Liang was a key driver of SMIC’s attempts to move into more advanced manufacturing nodes to catch up to the competition, rather than to double down on older but more profitable technology. On Tuesday, SMIC announced the appointment of Chiang Shang-Yi, a former executive at TSMC, as executive director.